Binding agents for photographic hydrophilic colloid layers which are crosslinked by treatment with alkalis



United States Patent 3,382,677 BINDING AGENTS FGR PHOTOGRAPHIC HYDR'O- PHILIC COLLOID LAYERS WHICH ARE CROSS- LINKED BY TREATMENT WITH ALKALIS Wolfgang Himmelmann, Cologne-Stammheirn, and Alexander Riebel, Leverhusen, Germany, assignors to General Aniline & Film Corporation, New York, N.Y., a corporation of Delaware N0 Drawing. Filed Jan. 6, 1965, Ser. No. 423,835 6 Claims. (Cl. 96-414) Many water-soluble, synthetic and natural polymers are known which are used as additives for protein containing photographic layers, such as silver halide emulsion layers or auxiliary photographic layers, in order to improve the properties of gelatin which is mainly used as the colloid of the layer. Many of these compounds have already been described as substitutes for gelatin in photographic silver halide emulsions but could not find acceptance because of their disadvantages. Gelatin itself has, together with many good properties, the disadvantage inter alia that it becomes extremely brittle at low humidity. It is therefore attempted to eliminate this fault by addition of appropriate high molecular materials. However when foreign substances are added in larger amounts to gelatin, it often happens that the gelatin thereby loses its property of irreversible gel-sol conversion, which is in no case desired but is very disadvantageous, since the entire technology of manufacturing photographic layers would have to be changed.

Moreover it has been long known to cross-link irreversibly the layer colloids of photographic silver halide emulsions-especially the proteins-by appropriate monomeric or polymeric compounds, in order to make the layer formers resistant to heat and especially to treatment baths. By such hardening, further disadvantages, especially for the photographic properties of the materials can arise, especially when one is compelled to attempt an intensive hardening by addition of foreign materials to the layer colloid. Thus, for example, stability in storage and swelling of the hardened photographic materials can be so modified that these materials are no longer usable for photographic reproduction. This is also mainly the case when hardening occurs during or directly after coating, and when hardening agents are used which no longer permit control in storage. Hardening agents have therefore been used which become effective only on treatment with alkaline baths but such materials have ordinarily no layer-forming properties and are moreover added to the gelatin only in small amounts.

Examples of other known polymeric additions and substitutes for gelatin are: polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyacrylic acid, copolymers of acrylic acid and 'acrylamide, copolymers of polyvinylpyrrolidone and acrylic acid, copolymers of vinyl alcohol and acrylic acid, naturally occurring materials such as dextrines, dextrans, amyloses, starch, alginic acid, gum arabic, pectines as well as other materials. As already in dicated, these materials can influence the photographic protein containing layer in a disadvantageous manner. In many cases an especially intensive hardening is necessary, particularly when the additives are used in larger amounts, whereby the original advantage of the gelatin substitutes is often lost.

It has now been found that addition products of high molecular weight hydroxyl group containing compounds with acrolein constitute especially valuable additives for photographic protein containing layers.

The special properties of these additives can be characterized in that their aqueous solutions can be added to the layer proteinespecially gelatinin such amounts that the layer colloid obtained contains 2 to 90% of the additive and that mixtures of the two components produced in this mixture ratio are irreversibly cross-linked by alkaline processing baths to water-insoluble but waterswellable compounds. The polymeric products used according to the invention, are distinguished on the one hand from the known high molecular weight hardening agents which can be added only in small amounts to the layer protein and cannot themselves be cross-linked by small amount of protein, and also, on the other hand, from the aforesaid additives which partly replace the layer protein but can then not be irreversibly cross-linked.

The production of the additives used according to the invention is known in German Patent 738,869. According to the latter, hydroxyl group containing polymeric compounds are reacted with acrolein in the presence or absence of solvents or diluents. The derivatives produced to be dissolved in water after precipitation or in some cas s reprecipitated with alcohol or acetone and used in this form. The addition products contain free aldehyde groups which can be determined by reaction with sulfite and ensuin' titration. The conclusion can thus be drawn that the reaction follows the course of 1,2-addition of the hydroxyl group to the carbon-to-carbon double bond of the acrolein.

As starting material for the preparation of addition products, hydroxyl group containing high molecular weight synthetic or naturally occurring compounds are essentially suitable which are soluble in water or mixtures of water with water-miscible organic compounds such as lower alcohol. Examples are polyvinyl alcohols or derivatives of polyvinyl alcohois, such as polyvinyl alcohols which are partly esterified by mono or polybasic carboxy acids, polysaccharides or derivatives of polysaccharides such as starch or starch derivatives, dextrine, cellulose derivatives such as carboxymethylcellulose, hydroxyethylcellulose, also glucosans and alginic acids. In order to prepare the addition products, the acrolein is preferably added in amounts from 0.5 to 3.0 parts by weight per part by weight of the hydroxy group containing high molecular weight compound. The reaction can take place in aqueous medium at pH values at from 9 to 10 at room temperature. The addition products can also be used in the form of sulfurous acid adducts. Preferred addition products are those of polyvinyl alcohols, dextrines, alginic acids and glucosans, or similar film-forming polymers.

For the preparation of photographic layers, the aqueous coating solutions which contain film-forming proteins and the aforesaid addition products, are adjustd to a pH value of 6 to 7.5 and thereupon cast on suitable supports and dried. Hardening of the layers results when these layers are treated with alkaline treatment baths, such as developer solutions, or with gaseous ammonia or amines. In this way, there are obtained layers which are fast to boiling and coatable even when the addition products are used in larger amounts than the proteins. The addition products to be used according to the invention are suitable for the preparation of image receiving layers for the silver salt diffusion process, since in this case layers are required which are strongly susceptible to swelling but nevertheless must have a certain strength in order to lead to acceptable results. It is of especial advantage that this can be done with the aid of the above-described addition products in a simple manner, so that in a single step, the desired copying layer is obtained. The addition products are also useful for the preparation of photographic blackand-white and color emulsions, and are compatible with the usual layer additives such as optical sensitizers, chemical sensitizers, etc.

The preparation of the above-described addition products is hereinafter first described, and following this, their use in specific examples.

Compound 1.-Addition product of dextrine and acrolein 22 grams of dextrine. are dissolved in 500 ml. water, and 16.6 ml. acrolein are added. The pH of the solution is adjusted with dilute aqueous caustic soda salts to 9-10. The mixture is agitated for 48 hours at room temperature, neutralized with dilute hydrochloric acid and the reaction product precipitated with 1500 ml. acetone. After reprecipitating three times from water with acetone, the derivative is dissolved in water and stored, with the addition of phenol, as a solution. The derivative contains 0.7% by weight of free aldehyde groups.

Compound 2.Addition product of dextrine and acrolein 22 grams of dextrine are reacted with acrolein as described for Compound 1, except that 12.5 ml. of acrolein is used. The derivative contains 0.5% free aldehyde groups.

Compound 3.Addition Product of Polyvinyl Alcohol and Acrolein 22 grams of polyvinyl alcohol are dissolved in 500 ml. water, whereupon 16.6 ml. acrolein are added to the s lution, the pH value is adjusted With dilute aqueous caustic salts to 9-10. After agitating 2 to 3 hours at room temperature and neutralizing with dilute hydrochloric acid, the condensate is separated by addition of 1000 ml. acetone. The product is rep recipitated from water with acetone three times and then dissolved in hot Water. The content of tree aldehyde groups amounts to 2.1%.

Compound 4.Addition Product of Laevoglucosan and Acrolein 22 grams of laevoglucosan are dissolved in 500 ml. water and reacted with 16 ml. acrolein -for 5 hours at room temperature. The pH value is adjusted to 9-10. The reaction temperature rises initially from 24 C. to 27 C. The mixture is neutralized with dilute hydrochloric acid and the reaction product is precipitated with 3000 m1. acetone. After reprecipitation twice the product is dissolved in hot water with a small amount of phenol, and stored as an aqueous solution.

Compound 5.Addition Product of Alginic Acid and Acrolein 60 grams of alginic acid are suspended in 540ml. water and agitated with a high speed agitator. The mixture is treated with sufficient 10% aqueous caustic soda that a solution is formed and the pH value is 12. After minutes the pH is adjusted by addition of glacial acetic acid to 10, and While vigorously agitating, 40 grams of distilled acrolein are added all at once. The pH value is maintained at 10 during 2 hours by adding 10% caustic soda solution, and then the mixture is allowed to stand over night. Upon adding 1500 ml. of acetone while agitating, the product is almost completely precipitated and can be air dried. For purification the derivative can be dissolved in hot water and again precipitated with acetone. It contains 1.6% free aldehyde groups and dissolves in Water to a highly viscous solution. The alginic acid used for the precipitation of Compounds 5 and 6 has a viscosity of 5 to 10 centipoises in 1% aqueous solution at C.

Compound 6.-Addition Product of Alginic Acid and Acrolein 60 grams of alginic acid are dissolved as was done in preparing Compound 5, but agitated at a pH of 12 for 6 hours. The pH is then brought to 10, and the mixture reacted with acrolein as described above. The product thus obtained contains 2.7% free aldehyde groups and dissolved in water to form a highly viscous solution.

Compound 7.Addition Product of Sodium Alginate (commercial product M'anucol) and Acrolein 30 grams of sodium alginate are dissolved with addition of aqueous caustic soda in 540 ml. water as described for preparation of Compound 5, and reacted with 20 grams of distilled acrolein. The product obtained by precipitation with 1500 ml. acetone contains 1.7%v free aldehyde groups and dissolves in Water to form a highly viscous solution. The sodium alginate has a viscosity of'25 to 30 centipoises in 1% aqueous solution at 20 C.

EXAMPLE I The following mixtures are prepared in two glass beakers:

(1) ml. of 6% aqueous solution of gelatin and 20 ml. of 6% aqueous solution of Compound 3.

(2) 20 ml. of 6% gelatin solution and 80 ml. of 6% aqueous solution of Compound 3.

Upon adding a small amount of caustic soda (pH 11l2) both solutions hardened within a short time to irreversible gels. If the mixtures are coated on glass plates before addition of caustic soda solution, and the layers are exposed to an ammonia atmosphere, they are after drying, resistant to boiling water and are no longer water-soluble. In the first case, the condensation produ'ct plays the role of cross-linking agent and in the second case, the gelatin performs this function. In both cases water-insoluble cross-linked products are obtained.

EXAMPLE II The following coating solutions are prepared:

(1) 5 00 ml. of -a silver chloride-silver bromide emulsion of medium sensitivity containing 60 grams of gelatin per 1000 m1. are mixed with 500 ml. of a 6% aqueous solution of Compound 2.

(2) 600 ml. of the same silver chloride-silver bromide emulsion is mixed with 400 ml. of a 6% solution of Compound 2.

(3) 500 ml. of the silver chloride-silver bromide emulsion are mixed 'with 500 ml. of 6% gelatin (control for 1).

(4) 600 ml. of the silver chloride-silver bromide emulsion are mixed with 500 ml. of 6% gelatin (control for 2).

All of the solutions are provided with the usual coating additives, other than a hardening agent, and coated on an acetylcellulose support which is prepared in the usual manner. After drying, the layers are developed for 2 minutes in Agfa developer, fixed for 8 minutes, watered for 30 minutes and thereupon the melting points of the layers are determined:

Layer melting point, C.

Test 1 100 Test 2 100 Test 3 38 Test 4 38 The photographic properties of Tests 1 and 2 are the same as those of Control Tests 3 and 4. No fog and no reduction in sensitivity occurs although 40 to 50% of the gelatin is replaced by a non-proteinaceous compound. Layers fast to boiling are obtained with good adhesion and good permeability for treatment baths. Instead of Compound 2, Compound 1 can be used.

EXAMPLE III The following coating solutions are prepared:

(1) 40 ml. of 1% solution of Compound 2 are added at pH value of 6 to 100 ml. of silver chloride-silver bromide emulsion containing 60 gr. of gelatin per 100 ml.

(2) 32 ml. of a 1% solution of Compound 2 are added at a pH of 6 to 100 ml. of the same silver chloride-silver bromide emulsion.

(3) 40 ml. of 1% gelatin at a pH 6 are added to 100 ml. of the same emulsion.

The solutions are provided with appropriate coating additives other than hardening agents, and coated on a Before Development C.) After Development C.)

Storage at Storage at Storage at Storage at Room 50 0. Room 50 0. Temperature 24 Hours Temperature 24 Hours Test 1 38 40 100 100 Test 2 88 52 100 100 Test 3 38 38 38 39 EXAMPLE IV A picture receiving layer for the silver salt diffusion process is prepared as follows:

100 ml. of a aqueous gelatin solution containing 0.006 gm. of colloidal silver sulfide and 10 grs. of sodium thiosulfate is adjusted to a pH 6.5 and treated with 0.5 ml. of 40% aqueous bisulfite solution; thereupon 100 ml. of a 5% aqueous solution of Compound 3 is added, together with 150 ml. of a 1% aqueous solution of carboxymethylcellulose, and the pH value of the mixture is adjusted to 6.8; the coating solution thus obtained is coated in the normal manner on ordinary paper and dried.

The positive material is led in contact with an imagewise light exposed negative layer (silver halide emulsion layer) prepared in the usual manner, through one of the known developing apparatuses which contains the following solution:

Water ml 1,000 p-Methylaminophenolsulfate gr 1.5 Hydroquinone gr Potassium bromide gr- 2 Sodium sulfite (anhydrous) gr 100 Sodium hydroxide gr 15 After 10 to seconds the two layers are separated, and there is obtained on the positive layer, after drying, a water and smudge fast picture.

EXAMPLE V Example IV was repeated except that 127 ml. of a 10% gelatin solution was used which contains per 100 ml. the

additives set out in Example IV as well as 100 m1. of a 7.1% aqueous solution of Compound 1 and 200 ml. of 1% c-anboxymethylcellulose solution. After processing, there is obtained a strong and resistant positive.

EXAMPLE VI 5 grs. of Compounds 5, 6 or 7 are dissolved in 263 ml. hot Water and treated with 100 ml. of 10% gelatin solution Which contains 0.008 grs. colloidal silver sulfide, 10 grs. of sodium thiosulfate as well as 0.5 1111. of 40% aqueous bisulfite solution-which is adjusted to a pH of 6.8. The solution is coated on ordinary paper and processed accordingly as described in Example 1V. There is obtained a resistant and well developed picture.

We claim:

1. A binder for photographic hydrop-hilic colloid layers which are susceptible to cross-linking upon alkaline treat ment, comprising a film-forming protein and an addition product of acrolein with a high molecular weight hydroxyl group-containing polymeric organic compound which is soluble in at least one of the solvents selected from the class consisting of ethyl alcohol and Water.

2. A rbinder as defined in claim 1 wherein said protein is gelatin and said hydroxyl group-containing organic compounds is selected from the class consisting of polyvinyl alcohols, polyvinyl alcohols which are partly esterificd with organic carboxylic acids, starch, dextrin, carboxyme-thyl cellulose, hydroxyethyl cellulose, glucosan and alginic acid.

3. A 'binder as defined in claim 1 wherein the proportion of said addition product contained therein ranges from 2 to by weight.

4. A binder as defined in claim 1 wherein said addition product is the reaction product of three parts by Weight of acrolein with one part by weight of said high molecular weight hydroxyl group-containing compound in aqueous medium at room temperature and at a pH value of 9-10.

5. Light-sensitive photographic material having a transparent film base, a silver halide emulsion layer containing a binder as defined in claim ll.

6; A copy receiving sheet for use in the silver salt diffusion process having a paper base and on a surface thereof, a layer of a binder as defined in. claim 1.

References Cited UNITED STATES PATENTS 2,652,345 9/1953 Jones 96-l11 XR 3,226,234- 12/1965 Himmelmann et a1. 96-111 FOREIGN PATENTS 1,183,372 12/1964 Germany.

NORMAN G. TORCHIN, Primary Examiner.

R. H. SMITH, Assistant Examiner. 

1. A BINDER FOR PHOTOGRAPHIC HYDROPHILIC COLLOID LAYERS WHICH ARE SUSCEPTIBLE TO CROSS-LINKING UPON ALKALINE TREATMENT, COMPRISING A FILM-FORMING PROTEIN AND AN ADDITION PRODUCT OF ACROLEIN WITH A HIGH MOLECULAR WEIGHT HYDROXYL GROUP-CONTAINING POLYMERIC ORGANIC COMPOUND WHICH IS SOLUBLE IN AT LEAST ONE OF THE SOLVENTS SELECTED FROM THE CLASS CONSISTING OF ETHYL ALCOHOL AND WATER.
 5. LIGHT-SENSITIVE PHOTOGRAPHIC MATERIAL HAVING A TRANSPARENT FILM BASE, A SILVER HALIDE EMULSION LAYER CONTAINING A BINDER AS DEFINED IN CLAIM
 1. 